Double patterning is a technology developed for lithography to enhance feature density in integrated circuits. Typically, the lithography technology is used for forming features of integrated circuits on wafers. The lithography technology involves applying a photo resist and defining patterns in the photo resist. The patterns in the photo resist are first defined in a lithography mask, and are implemented either by the transparent portions or by the opaque portions of the lithography mask. The patterns in the lithography mask are transferred to the photo resist through an exposure using the lithography mask, followed by the development of the photo resist. The patterns in the patterned photo resist are then transferred to the manufactured features, which are formed on a wafer.
Various techniques have been created to implement double or multiple patterning. One technique is a lithography-etch-lithograph-etch (LELE) technique. In a LELE technique, a pattern is generally divided into multiple parts to be implemented using multiple, respective lithography followed by etch steps. Another technique is a self-aligned technique. In a self-aligned technique, a pattern is generally formed by forming a mandrel and spacers on sidewalls of the mandrel, where the spacers are the pattern to be formed in the underlying substrate. In these techniques, the goal is to decrease a width between neighboring features, thereby increasing density.